This invention relates to an apparatus for automatically controlling a blade of earth working equipment such as a bulldozer.
The following proposals have been made in the art of automatic controlling of blades of earth working equipment:
1. The specification of U.S. Pat. No. 2,796,685 discloses a method for controlling a position of a construction equipment by forming parallel radiation energy planes and automatically controlling the position of the equipment in accordance with deviation from the energy planes.
2. The specification of U.S. Pat. No. 2,916,836 discloses a method according to which a reference plane is formed by rotating a visible radiation source and detecting light by a light receiving device attached to a blade for controlling the blade by means of a motor or a hydraulic system using an electromagnetic valve.
It will be difficult to achieve the control as described in the patent by this method in view of the response speed realized by this method, for the light source is a lamp and the light receiver can detect only a vertical position.
3. The specification of U.S. Pat. No. 3,000,121 discloses a system for automatically controlling a blade of a construction equipment in a vertical direction in which a reference plane is formed by a light beam and a light receiver is provided for detecting whether the center of the light receiver coincides with the center of the reference light beam and emitting a signal of a different polarity depending upon whether the center of the reference light beam is above or below the center of the light receiver.
4. The specification of U.S. Pat. No. 3,887,012 discloses a circuit for controlling an earth working equipment which, in a device having a certain relation with a plane formed by narrow rotating beam of radiant energy of a fixed wavelength, a receiver has at least three channels and a light receiving element cathodes a light beam incident from all directions within 180.degree. or 360.degree. thereby to control the earth working equipment so that the light receiving element catches the light beam at its center.
The proposed circuit is mainly directed to the control of a motor grader and is not convenient for application to a bulldozer in which light beams may enter two channels simultaneously.
5. There has also been proposed a device which, in an apparatus for detecting height of a laser beam emitted from the laser emitter by a beam receiver and controlling a blade by driving an electromagnetic valve, prevents stopping of an engine when an excessive load is applied.
It is an object of the invention to provide a control apparatus capable by controlling lifting, lowering and turning of the beam receiver effectively and enabling the beam receiver to face the beam projector directly regardless of direction of the equipment.
It is another object of the invention to provide a control apparatus in which even if a laser beam is deviated from the beam receiver, the deviation is promptly corrected so that the beam receiver can catch the laser beam again.
It is still another object of the invention to provide a control apparatus in which height of the beam receiver relative to the blade can be adjusted so that the level of the blade can be controlled very accurately.